In fields such as combinatorial chemistry and autosampling, it is well known for a large number of containers or vessels to be held in a regular array of rows and columns or in concentric circles.
In life science chemistry, for example, it is known to use a moulded block formed with an array of wells, each well forming a container for a different combination of chemicals. It is known to provide a lid for such a block which is in the form of a fairly stiff mat formed with an array of plugs for closing the wells. The blocks are usually moulded from plastic material but in combinational chemistry where the chemicals being analysed are often incompatible with this (such as when organic solvents are involved), it has been proposed to form the block from glass, or to provide a glass vial as a liner to each well. In the latter solution, each glass vial is provided with its own separate cap (which may be a crimp cap or a snap-fitting cap) which must be individually fitted to the vial. When a needle is inserted through the cap to remove a sample from the vial, it is gripped by the cap and the vial tends to be withdrawn from the block when the needle is being removed.